Balun using two Lange Couplers
How to treat "EN1" terminal ?
Loaded?, Open?, Short?
Terminated Network so 50 Ohm.
What behavior will be if "EN1" is open or short ?
Load at "EN1" is for adujusting balance ?
Especially magnitude ?
In fact Lange Coupler is a kind of Directional Coupler ( it's also called Multiconductor Coupler) so you can consider it being as a "Folded Directional Coupler" ( not exactly but roughly )
As you know well, Directional Couplers are 4-Ports Devices and one port should be terminated for Magnitude and Phase Balance.Phase Balance is more sensitive in Lange Couplers because The Ouputs are Quadrature.There may be also some Phase Balancing elements such as Adjustable Transmission Line terminated by X Ohm rather than 50 Ohm.
One port is not terminated clearly for each Lange coupler in this balun.
They are node 1 and node 5.
I think this balun?s operation is actually same as Marchand balun.
If so, ?EN1? should be open.
EN1 means-I think- Equalization Network.Because this is not a standard back-to-back connected Balun configuration,Regarding to my simulation, it has a Bandpass characteristic.